Dr. Valdes-Morales, Hector

2024, Dr. Valdes-Morales, Hector, Govinda raj, Muniyandi, Sundaram-Ganeshraja, Ayyakannu, Kaviyarasan, Kulandaivelu, Pugazhenthiran, Nalandhiran, Katayama, Kenji, Theja-Vaskuri, Chandra, Bosco, Aruljothy, Neppolian, Bernaurdshaw

Antibiotic overuse and indiscriminate disposal ultimately lead to overexploitation of the ecosystems expanding requirements, producing significant environmental and biological consequences. Advanced oxidation processes (AOPs) have kindled the interest of many researchers in targeting the destruction of antimicrobial and waterborne pollutants. As a result, an improvement of low-cost, high-efficiency photocatalysts for the successful decomposition of antibiotics is critical for the cleaning of harmful contaminants in rivers and lakes. In the current work, a simple hydrothermal approach was used to create the bismuth vanadate nanoballs (BiVO4) anchored to the exterior of the ultrathin g-C3N4.It was named g-C3N4/BiVO4(X) (X = 5, 10, 15, and 20%) nanocomposites, and the photocatalytic removal of ciprofloxacin (CPX) and amoxicillin (AMX) was investigated using synthesized composites. According to the advanced characterization techniques, the synthesized composites exhibit superior purity and crystalline nature. The electron transfer occurring within the g-C3N4, in conjunction with the extension of BiVO4 nanoballs, enhances the generation of photoexcited electron−hole (e−/h+) pairs. This phenomenon contributes significantly to the improved photocatalytic activity observed in the g-C3N4/BiVO4 system. Furthermore, the photocatalytic efficiency exhibited by g-C3N4/BiVO4(10%) nanocomposites in antibiotic removal surpasses that of both bare materials and other composite counterparts. The elimination of antibiotics was aided by reactive oxygen species (ROS)such as O2•−, h+, and OH. Finally, g-C3N4/BiVO4(10%), the intermediate byproduct of CPX and AMX decomposition, was discovered, and a probable CPX and AMX removal route was postulated. The g-C3N4/BiVO4(10%) composite exhibits long-term stability after five cycles. This study applies a green and ecologically responsive technique to the development of high-performance photocatalysts for wastewater remediation.

2022, Dr. Valdes-Morales, Hector, Pugazhenthiran, Nalandhiran, Mangalaraja, Ramalinga, Sathishkumar, Panneerselvam, Murugesan, Sepperumal

In this work, crystal facets, bandgap, size and shape of reduced graphene oxide (rGO) modified anatase {001} black TiO2 nanosheets (rGO-B-TiO2 NSTs) were tailored for the photocatalytic oxidation of ethylene under high humidity content. XRD, Raman and HR-TEM analyses confirm that rGO-B-TiO2 NSTs have a 94 % of exposed {001} facets with high number of oxygen vacancies. In addition, rGO-B-TiO2 NSTs exhibit increased values of surface area and porosity compared to its pristine form. A 48 and 34 μmol g− 1 of ethylene are adsorbed at the surface of rGO-B-TiO2 NSTs in the absence and in the presence of humidity, respectively. In addition, operando DRIFTS analyses provide the insight of surface interactions between ethylene molecules and adsorption sites of rGO-B-TiO2 NSTs. The photocatalytic removal efficiencies of the synthesized materials under both UV and visible light irradiation proceed as follows: rGO-B-TiO2 NSTs > B-TiO2 NSTs > TiO2 NSTs > commercial TiO2 NPs. Further, ethylene is very quickly photocatalytic oxidized when rGO-B-TiO2 NSTs is applied under UV light irradiation, having a 72 and 92 % ethylene removal in the absence and in the presence of humidity, respectively. Moreover, a 48 and 58 % of ethylene removal takes place in the absence and presence of humidity under visible light irradiation, respectively. Results indicate that rGO-B-TiO2 NSTs boost the photocatalytic activity through their virtue of visible-light absorption properties (Bandgap = 2.61 eV) and the rapid electron-hole separation at the rGO {001} black TiO2 NSTs interfaces. Such findings are confirmed through UV-visible diffused reflectance, photoelectrochemical and photoluminescence analyses. Nanosheets made of rGO modified {001} black TiO2 could be used as an effective photocatalyst for the removal of ethylene from large volume fruit storage areas by exploiting a simple light source in the presence of high content of humidity.

2023, Dr. Valdes-Morales, Hector, Shanmugaraj, Krishnamoorthy, Vinoth, Victor, Pugazhenthiran, Nalandhiran, Salvo, Christopher, Sepúlveda, Erwin, Viswanathan-Mangalaraja, Ramalinga

We report the synthesis of a new range of ferrihydrite-graphene oxide (FH-GO) foams using chitosan as cross linker, with varying iron content (5 wt%, 10 wt%, and 20 wt% of FH) as highly efficient adsorbents for the removal of arsenic (III) (As(III)) in an aqueous solution. The sonochemical methods were adopted to synthesize various FH-GO foams and were further characterized by XRD, SEM, TEM, FTIR, Raman, and XPS techniques. The synthesized materials were used for the removal of As(III) in both batch and fixed bed absorbent column methods. The adsorption isotherm results showed that the 10 wt% of FH-GO foams demonstrated a superior adsorbent for the As(III) with high adsorption capacities than that of the other two FH-GO foams (5 wt% and 20 wt% of FH). Moreover, 10 wt% of FH-GO foams was also demonstrated to be nearly a complete (>98.4%) removal of As(III) ions at neutral pH 7. The adsorption isotherm fitted very well with the Langmuir model with the highest accuracy data for all the synthesized adsorbent materials. In addition, the fixed bed absorbent column method was also adopted for the removal of As(III) ions in the water sample, which showed > 99.2% of removal efficiency. The outstanding adsorption capabilities, along with their easy and low-cost synthesis, make these kinds of adsorbents extremely capable for commercial applications in wastewater treatment and drinking water purification.

2023, Dr. Valdes-Morales, Hector, Vinoth, Victor, Kaimal, Reshma, Selvamani, Muthamizh, Michael, Rubina, Pugazhenthiran, Nalandhiran, Viswanathan-Mangalaraja, Ramalinga, Anandan, Sambandam

In this work, a facile green approach for the synthesis of graphene quantum dots (GQDs) embedded on silicate network silver nanocrystals (GQDs-AgNCs(APTS)) is reported. Moreover, glassy carbon-GC electrodes were modified with the prepared nanocomposite containing graphene quantum dots supported on silver nanocrystals (GQDs-AgNCs(APTS)) and applied for simultaneous detection of guanine (GA) and adenine (AD). The chemically modified electrode was assessed during the determination of purine bases by cyclic voltammetry-CV and differential pulse voltammetry-DPV. The incorporation of GQDs-AgNCs(APTS) nanocomposites over the surface of the GC electrode considerably enhances the anodic peak currents and decreases the adenine and guanine peak potentials. Compared to other electrodes, GQDs-AgNCs(APTS)/GC improved the electrochemical behavior towards the detection of adenine and guanine. At optimal conditions, calibration curves were obtained by DPV being linear in the range of 0.1–6.0 μM and 0.1–5.0 μM for guanine and adenine, respectively. The detection limits of both guanine and adenine were estimated as 0.1 μM. Additionally, interferences analyses were performed on the existence of other interferent compounds. Furthermore, the method developed for the identification of GA and AD was proved using fish sperm DNA samples.

2020, Dr. Valdes-Morales, Hector, Pugazhenthiran, Nalandhiran, Mangalaraja, R., Vijaya, S., Suresh, S., Kandasamy, M., Sathishkumar, P., Gracia-Pinilla, M., Murugesan, S., Anandan, S.

A facile, fluorine-free and non-toxic one-pot solvothermal technique was adopted to synthesis TiO2 nanoflowers with anatase phase having 98% highly exposed {001} facets (TiO2 {001} NFs). The morphology, grain size and crystallinity of pure TiO2 {001} NFs and reduced graphene oxide (RGO) sheets modified TiO2 {001} NFs (RGOTiO2 {001} NFs) were inspected by diffuse reflectance spectroscopy (DRS), X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM images showed the development of anatase TiO2 {001} NFs with high crystallinity and uniform shape. The influence of RGO on the performance of the TiO2 {001} NFs as a photoanode material in dye-sensitized solar cell (DSSC) was examined. High energy conversion efficiency (ɳ) was observed for the DSSC based on a photoanode made of RGO-TiO2 {001} NFs when compared to DSSCs based on photoanodes fabricated using pure TiO2 {001} NFs and commercial Degussa P25 TiO2, which exhibited η of 6.78, 4.59 and 2.71%, respectively. The improved performance of the DSSC based on a photoanode composed of RGOTiO2 {001} NFs was due to its good crystallinity, high dye intake and enhanced light-harvesting properties. Moreover, the presence of RGO greatly hindered the recombination of photogenerated electrons and increased their lifespan. This work discloses a novel efficient photoanode design for improving performance of the DSSCs.

2023, Dr. Valdes-Morales, Hector, Vinoth, Victor, Shanmugaraj, Krishnamoorthy, Pugazhenthiran, Nalandhiran, Salvo, Christopher, Anandan, Sambandam, Mangalaraja, Ramalinga

The goethite (α-FeOOH) nanoparticles were wrapped on the reduced graphene oxide (rGO) to synthesize the α-FeOOH/rGO nanocomposites. The nanocomposites (NCs) were initially examined for their optical, structural, and morphological properties. The XRD data obtained the crystallite size of the α-FeOOH, showed that the average crystal size for pristine α-FeOOH and α-FeOOH/rGO nanocomposites were about 85 and 90 nm, respectively. The transmission electron microscope confirmed the nanoparticles (NPs) were evenly distributed throughout the reduced graphene oxide sheets. The nanocomposites improved glassy carbon electrodes (GCE), making them efficient sensors for detecting the arsenic(III) (As+3) in a pH 5 phosphate buffer solution with an Ag/AgCl reference electrode. The detection limit for As+3 was 0.07 μgL−1 and the resulting sensitivity was 0.39 μA−1 μgL−1 in the linear dynamic range of 0.1–10 μgL−1. The α-FeOOH/rGO/GCE was more sensitive than its original and showed a synergistic effect due to the influence of α-FeOOH on the properties of rGO. The α-FeOOH/rGO NCs-modified GCE electrode performed as a promising sensor, by separating the common interfering ions. Moreover, the modified electrode exhibited remarkable stability, repeatability, and potential real-time application towards the detection of arsenic(III). Additionally, the proposed approach has been successfully applied to the detection of As+3 in the real water sample.